Avidity Biosciences Sets Atrium Spinoff Ahead of Novartis Buyout

Avidity Biosciences – the San Diego rare disease biotech being acquired by Novartis for $12 billion – is spinning off its early-stage cardiology unit into a new company called Atrium Therapeutics. In a move that gives Avidity’s shareholders a parting gift as they surrender the rest of the company to Novartis, Avidity’s board designated February 12, 2026 as the record date (close of business, Eastern Time) for the pro rata distribution of Atrium shares (PR Newswire). Each Avidity holder on that date will receive one share of Atrium for every ten shares of Avidity held. The distribution date is expected to be February 26, 2026, just ahead of Novartis closing the merger on February 27 (SEC filing).

This spinoff isn’t just a nice gesture; it’s a requirement to seal the Novartis deal. Avidity’s early-stage precision cardiology programs – assets Novartis evidently didn’t covet – must be separated into Atrium prior to the acquisition (Fierce Biotech). Avidity convened a special shareholder meeting on Feb. 23 only to immediately adjourn it, giving a few extra days to finalize conditions for the Atrium share distribution (Investor release). The meeting will reconvene Feb. 26, the same morning Atrium shares drop into accounts. The spinoff distribution is a condition to closing the $72-per-share Novartis buyout, so no spin, no deal. To smooth the process, Avidity’s stock (NASDAQ: RNA) will temporarily trade under the ticker “RNAM” around the distribution date.

So what exactly are Avidity holders getting in Atrium? Atrium Therapeutics will house Avidity’s rare disease cardiology pipeline – essentially everything in precision cardiomyopathy that’s too nascent for Novartis’s taste. That includes preclinical candidates ATR-1086 and ATR-1072, targeting rare genetic heart disorders like phospholamban (PLN) cardiomyopathy and PRKAG2 syndrome. Atrium also inherits Avidity’s existing partnerships in the cardio space, including collaborations with Eli Lilly and Bristol Myers Squibb (Endpts News).

Atrium comes pre-capitalized and with familiar faces at the helm. Avidity will capitalize the spin-off with about $270 million in cash. Kathleen Gallagher, Avidity’s Chief Program Officer, will become CEO of the new company. Avidity CEO Sarah Boyce will serve as board chair. This leadership continuity and war chest should give Atrium a solid start. The spinoff will be taxable to recipients, so investors will want to talk to their tax advisor before celebrating that freebie too hard.

Avidity’s stock jumped over 40% on the buyout news, reflecting the rich premium. Now investors are watching to see what their Atrium stub might be worth. One person’s leftover is another’s lottery ticket, and this rare disease biotech spinoff is about to scratch off a new set of numbers.

Disclosure: The author holds no position in any stock mentioned